PR: Make QIcon.ThemeIcon enum for Qt < 6.7

[StSav012]

In Qt 6.7, they finally added icons from https://specifications.freedesktop.org/icon-naming-spec/latest/ as a collection of constants. Years of looking the names up are over.

I haven't implemented NThemeIcons because I have no idea how to do it for string constants.

Overview of the icons

import sys

from qtpy import PYQT4, PYQT5, PYQT6
from qtpy.QtCore import Qt
from qtpy.QtGui import QIcon
from qtpy.QtWidgets import (
    QApplication,
    QGridLayout,
    QScrollArea,
    QToolButton,
    QWidget,
)


def kebab_case(name: str) -> str:
    """Convert a PascalCase name or a camelCase one to a kebab-case synonym."""
    return "".join((("-" + c.casefold()) if c.isupper() else c) for c in name).lstrip("-")


# A hotfix to be PRed later, see https://t.me/qtforpython/24462
if PYQT4 or PYQT5 or PYQT6:
    # Make the app instance last
    class QApplication(QApplication):
        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            QApplication._instance = QApplication.instance()


QApplication(sys.argv)
w: QWidget = QWidget()
layout: QGridLayout = QGridLayout()
w.setLayout(layout)

icon_button: QToolButton
for index, (key, value) in enumerate(QIcon.ThemeIcon.__members__.items()):
    icon_button = QToolButton(w)
    icon_button.setIcon(QIcon.fromTheme(value))
    icon_button.setText(key)
    icon_button.setToolButtonStyle(Qt.ToolButtonStyle.ToolButtonTextBesideIcon)
    icon_button.clicked.connect(lambda is_pressed, _key=key: print(_key) or QApplication.clipboard().setText(_key))
    layout.addWidget(icon_button, index, 0)

    free_desktop_org_key: str = kebab_case(key)
    icon_button = QToolButton(w)
    icon_button.setIcon(QIcon.fromTheme(free_desktop_org_key))
    icon_button.setText(free_desktop_org_key)
    icon_button.setToolButtonStyle(Qt.ToolButtonStyle.ToolButtonTextBesideIcon)
    icon_button.clicked.connect(
        lambda is_pressed, _key=free_desktop_org_key: print(_key) or QApplication.clipboard().setText(_key),
    )
    layout.addWidget(icon_button, index, 1)

    # Test that it's the same icon
    assert QIcon.fromTheme(value).cacheKey() == QIcon.fromTheme(free_desktop_org_key).cacheKey()

s: QScrollArea = QScrollArea()
s.setWidget(w)
s.show()
QApplication.exec()

[coveralls]

coverage: 91.311% (+1.1%) from 90.18%
when pulling 12d1f31 on StSav012:theme-icon-enum
into cd0b49b on spyder-ide:master.